Nonfluorescent negative stain for alanopine dehydrogenase activity on starch gels.

A two-step procedure for negative staining NADH-dependent alanopine dehydrogenase (ALPDH) activity on starch gels is described, using nitroblue tetrasolium and phenasine methosulfate. This method gives a blue background with unreacted NADH, and white areas where ALPDH is located. Using this technique the first reliable evidence of the existence of true ALPDH isoenzymes is obtained.